As demands for wireless multimedia services of users increase, the limited wireless resources are more important, thereby promoting the rapid development of more reasonable and efficient utilization of wireless resources in communication techniques. However, there is a difficulty that licensed spectrums cannot be used completely by primary users (wireless users qualified to use the licensed spectrums) due to a presenting existing fixed spectrum allocation strategy. In this case, there appears a concept of cognitive radio. The cognitive radio enables secondary users (i.e. wireless users not qualified to use the licensed spectrums) to find out more available spectrum resources by their interactions with wireless environments and to dynamically change operation parameters of the wireless environments to effectively utilize these resources, with influences on the primary users in a restriction scope.
A cognitive radio network comprises a primary network comprising a primary user (PU) and a primary base station (PBS) and a secondary network comprising a secondary user (SU) and a secondary base station (SBS).
The PU is authorized to use network resources, for example, the licensed spectrums in the networks, by the coordination of the PBS. The transmissions of primary network nodes (including the PU and the PBS) are subjected to zero interference of signals of secondary network nodes (including the SU and the SBS) or allowable interferences. Due to no cognitive radio function provided for the primary network nodes, it is to be ensured that the primary network nodes can be operated normally in no awareness of existence of the secondary network.
The secondary network may use the network resources of the primary network, for example, the licensed spectrums, when and only when the influences of the signals of the secondary network nodes on the primary network nodes are restricted in a scope. The spectrums using of the SU are controlled by the SBS generally. The secondary network nodes have the cognitive radio functions including spectrum sensing and analysis, spectrum management and switching, and spectrum allocation and sharing. The cognitive radio network may comprise one or more secondary networks where communication between the SU and the SBS may be implemented. A spectrum coordinator (SC) is used for management generally in the case that a plurality of secondary networks may share the spectrums. The SC collects operation information of each secondary network and provides resource allocation in order to realize efficient and fair resource sharing among the secondary networks. There is no direct information interaction between the primary network and the secondary network for improving the flexibility of the secondary network and the convenience of layout thereof. The secondary network nodes sense, detect and monitor the licensed spectrums to adjust the resources used thereby and the related system configurations, thus sharing the resources without influences on the primary network nodes.
The SU has an opportunistic feature for using the licensed spectrums so that the wireless resources are classified in a transmission opportunity (TO). The TO is a subset of primary system resources and may comprise one or more than one allocation units of the primary system resources, for example, a TO in a frequency division multiple access (FDMA) network corresponds to one or one group of frequency bands, a TO in a time division multiple access (TDMA) network corresponds to one or one group of time slots; and a TO in an orthogonal frequency division multiplexing (OFDM) network corresponds to one or one group of resource blocks (RB). The allocation of the licensed spectrums to the SU depends on a mode of using the licensed spectrums by the primary network, specifically, whether each TO may be used by the PU, which is referred to resource use status information of the primary network (called a primary network status or network status for short).
There is a challenge for the cognitive radio that the use mode of the licensed spectrums is complicatedly random for the SU due to lack of spectrum allocation information of the PU so that it is hard for the SU to effectively allocate the licensed spectrums.
Solutions concerning ensuring the SU in the network may use the network resources without influences on the PU have been provided. However, those solutions involve optimization of spectrum allocation and also determination of the way to use the network resources based on the fact that the PU has used resources. Those solutions are performed after the resources have been allocated to the PU; and the spectrums are optimized with the aid of a complex algorithm, accordingly, it will take a longer time to determine which network resources the SU may use so as to latterly allocate the resources, so that the TOs of valid data by a secondary system using the licensed spectrums are decreased, and hence it is hard to improve the use efficiency of the licensed spectrums.
Further provided is a solution comprising an information storage and management method which is taken to record statistic data of network operation statuses and a statistics-based resource allocation method where statistic information that the licensed spectrums are used by the PU is utilized to guide the allocation of the licensed spectrums to the SU. However, in such solution, association of the use statuses of the licensed spectrums in a spatiotemporal pattern is neglected so that the availability of the licensed spectrums for the SU may not be predicted more accurately. Therefore, the time and overheads required for the sensing operation may increase in order to ensure the allowable interferences of the SU on the PU. This will reduce the TOs of the valid data by the secondary system using the licensed spectrums, thereby causing failure of improving the use efficiency of the licensed spectrums.
No effective solution is provided for solving the problems of hysteresis and inaccuracy in the related techniques when the way of the SU to use the network resources is determined.